Caster



FIG. 1 is a top, rear and side perspective view of a caster, showing my new design;

FIG. 2 is a side view thereof, with the opposite side view being a mirror image thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a top view thereof; and,

FIG. 6 is a bottom view thereof. 

The ornamental design for a caster, as shown and described. 